Study Finds a Link Between Fatty Acid Ratios and Breast Cancer

June 1, 1996

WASHINGTON--A study of European women suffering from breast cancer has raised the intriguing possibility that the ratio of omega-3 to omega-6 polyunsaturated fatty acids (PUFA) may provide a way to predict an increased risk of the malignancy.

WASHINGTON--A study of European women suffering from breast cancerhas raised the intriguing possibility that the ratio of omega-3to omega-6 polyunsaturated fatty acids (PUFA) may provide a wayto predict an increased risk of the malignancy.

"We have looked at the balance between the two," saidepidemiologist Neil Simonsen, PhD, of the University of NorthCarolina at Chapel Hill, School of Public Health. "When wedo that, the ratio of omega-3 to omega-6 appears to be important.The higher the ratio, the more protective."

Therefore, he said, the balance between the two forms of PUFAsmay prove more relevant to the etiology of breast cancer thanthe absolute intake of a single fatty acid class.

Dr. Simonsen described the findings at Experimental Biology 96,an annual meeting of biological and biomedical researchers.

The PUFA ratio picture emerged from an analysis Dr. Simonsen conductedwith colleagues at the University of North Carolina and in Europe,which failed to confirm laboratory suggestions that a diet highin omega-6 fatty acids enhances mammary tumor activity.

The omega-6 fatty acids constitute the most common PUFA groupand include fats from corn oil and other vegetable sources. Thesecond PUFA family, omega-3, is found in fish, primarily oceanfishes.

Dr. Simonsen and his colleagues used data from EURAMIC (EuropeanStudy of Antioxidants, Myocardial Infarction, and Breast Cancer),a case-control investigation involving men and women. As partof the EURAMIC trial, investigators needle-biopsied adipose tissuefrom participants' buttocks to determine the antioxidant and fattyacid content.

Women From Five Nations

The researchers analyzed data from 698 women from five nations--Germany,Switzerland, Spain, The Netherlands, and Northern Ireland. Thesample included 291 women with primary breast cancer and 407 controlsselected from the same hospital catchment areas as the patients.

All were postmenopausal, with no major change in their weight,diet, or antioxidant use in the previous year. Other risk factorsfor breast cancer were considered in the analysis, including age,postmenopausal estrogen therapy, oral-contraceptive use, currentalcohol consumption, smoking status, parity, and age at menarcheand menopause.

Overall, the data indicated a statistically significant associationbetween higher concentrations of omega-6 in adipose cells andbreast cancer, but this was due to a high correlation found inone country--Spain. "If you exclude the patients from theSpanish center, the association goes away," he said.

An explanation may lie in the Spanish diet, which is high in oliveoil. Several studies have reported a protective association witholive oil consumption in southern European populations. The researchersfound that the Spanish women who had high levels of omega-6 alsohad low levels of oleic acid, a monounsat-urated fat dominantin olive oil--and vice versa.

The results for the Spanish women could indicate a reduction insome protective mechanism that eating olive oil provides, ratherthan a linkage between omega-6 and breast cancer, he said.

"It's hard to say that at the Spanish center that the findingis due to omega-6 and not to olive oil," Dr. Simonsen said."You see the same pattern whether you look at increasinglevels of polyunsat-urates or decreasing levels of oleic acid."

Right now, he said, "it's hard to make a smoking-gun recommendationfor clinicians." The new data may be making a further casefor olive oil, he said, "but we don't know if it's oliveoil or something else in that Mediterranean diet."

The study's most intriguing finding, in his view, is the possibilitythat the key factor in determining risk lies in the ratio of omega-3to omega-6.

The researchers are now in the midst of a more in-depth analysisof the omega-3/omega-6 ratio and other differences between thetwo PUFAs. They see this as more likely to provide illuminatinganswers than focusing on one fatty acid at a time. They also hopeto gain greater insights into the role of oleic acid and breastcancer.

"The real take-home message is that focusing in on just oneindividual type of fatty acid may not be the way to go,"Dr. Simonsen said. "We've got to look at the relationshipsbetween the different types."